Non-invasive coronary flow reserve is an independent predictor of exercise capacity after acute anterior myocardial infarction

Background. - After acute myocardial infarction (MI) coronary microvascular impairment and reduced exercise capacity are both determinant of prognosis. Objective. - We tested whether non-invasive coronary flow reserve (CFR) performed after MI predicts post-MI exercise capacity (EC). Methods. - Fifty consecutive patients (pts) (mean age 56.5 +/- 11 years, 30% women) with a first reperfused ST-elevation anterior MI, and sustained TIMI 3 flow after mechanical reperfusion, underwent prospectively non-invasive CFR in the distal part of the left anterior descending artery (LAD), using intravenous adenosine infusion (0.14 mg/kg per minute, within 2 min), within 24 h after successful primary coronary angioplasty (CFR 1), and 4 +/- 1.6 months later after a period of convalescence and a cardiac rehabilitation program (CFR 2). CFR was defined as peak hyperaemic LAD flow velocity divided by baseline flow velocity. All pts also underwent semi-supine exercise stress echocardiography (ESE) the same day of CFR 2. ESE was performed at an initial workload of 25-30 watts with a 20 watts increase at 2-minute intervals. Beta-blockers were withheld 24 h before ESE. Results. - The mean CFR 2 increased significantly when compared to CFR 1 (2.9 +/- 0.65 versus 1.9 +/- 0.4, P < 0.01). During ESE, percentage of maximal predict heart rate achieved was 82 +/- 12%, maximal workload 95 +/- 30 watts, exercise duration 486 +/- 155 s, the ratio of double product 3.1 +/- 0.8, and EC 5.8 +/- 1.1 metabolic equivalents. No ischemia was induced during ESE in all pts, and the degree of mitral regurgitation did not differ significantly between rest and exercise. CFR 2 was significantly correlated to all indices related to EC (all, P < 0.01), whereas CFR 1 was correlated to LV systolic function at follow-up (P < 0.05) but not to EC. In multivariate analysis including age, sex, and body mass index, CFR 2 remained an independent predictor of EC (P < 0.01). Conclusion. - Contrarily to acute CFR, CFR at follow-up is an independent predictor of EC after reperfused anterior MI. This suggests that the improvement of the coronary microcirculation is closely linked to the physical aptitude after MI. (C) 2012 Published by Elsevier Masson SAS.